Various abbreviations that appear in the specificaton and/or in the drawing figures are defined as follows:
3GPP third generation partnership project
ACK acknowledge
CAZAC constant amplitude zero autocorrelation code
CCE control channel element
CDM code division multiplex
CQI channel quality indicator
DL downlink
DM demultiplex
eNode B base station of an EUTRAN/LTE system
EUTRAN evolved UTRAN (also referred to as LTE or 3.9G)
FDD frequency division duplex
LTE long term evolution
ITU international telecommunication union
ITU-R ITU radiocommunication sector
LA location area
NACK negative ACK
OFDMA orthogonal frequency division multiple access
PUCCH physical uplink control channel
PDCCH physical downlink control channel
Rel. 8 3GPP Release 8
Rel. 9 3GPP Release 9
SRI scheduling request indicator
UE user equipment
UL uplink
UTRA universal mobile telecommunication system terrestrial radio access
UTRAN UTRA network
A proposed communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE, E-UTRA or 3.9G) is currently under development within the 3GPP. The current working assumption is that the DL access technique will be OFDMA, and the UL access technique will be SC-FDMA.
One specification of interest to these and other issues related to the invention is 3GPP TS 36.211, V8.2.0 (2008-03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Physical Channels and Modulation (Release 8), which is incorporated by reference herein in its entirety.
There is an increased focus on extending and optimizing the 3GPP LTE Rel. 8 radio access technologies for providing higher data rates at very low cost. These teachings are relevant to LTE-Advanced system (LTE-A) which will most likely be part of LTE Rel. 10. LTE-A will be a local area optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping the backward compatibility with LTE Rel 8. 3GPP has initiated a study item on LTE-A. It is commonly understood that SU-MIMO with 2 or 4 transmission antennas at the UE will be part of LTE-A [see for example LTE Advanced Workshop; Summary of LTE Advanced Requirements presented at the Workshop, Source: 3GPP TSG RAN Chairman; Doc. Number REV-080058].
It can be assumed that higher data rates set also increased requirement for control signalling. The UL control signals such as ACK/NACK, CQI and Scheduling request are transmitted on PUCCH (Physical Uplink Control Channel) in the absence of UL data. On PUCCH different UEs are multiplexed in the same frequency- and time resource by means of CDM. The above referenced 3GPP TS 36.211 describes two ways of achieving that multiplexing: using different cyclic shifts of the same base CAZAC sequence (which is described with reference to PUCCH formats 2a and 2b); and/or using different time domain spreading code between blocks of symbols (which is described with reference to PUCCH formats 1a and 1b). These formats are detailed at Appendix A, which includes the relevant sections 5.4.1 through 5.4.3 of the above-referenced 3GPP TS 36.211 document and definitions, symbols and abbreviations used therein.
Instantaneous channel state required for closed loop schemes is not available on PUCCH (FDD mode), and so open loop transmission is considered herein. Such an implementation needs to address two issues: UL measurement capability; and DL signalling arrangement. It is noted that it may be possible to arrange a few closed-loop signalling bits in the DL resource allocation grant transmitted on PDCCH (at the expense of system complexity and DL overhead), at least in the case when ACK/NACK signalling is related to dynamically scheduled DL data. However, economical arrangement of the needed measurement capability appears difficult if not impossible.
Open loop transmit diversity needs orthogonal resources for different transmit antennas (otherwise, the transmit antennas will interfere each other). Due to the fact that CDM type of access is being used in the Rel. 8 PUCCH there is no additional (symbol) space available for the space time coding (this is the case in both frequency and time domain). Multiplexing capacity of ACK/NACK channel is limited by the number of reference signal (RS) sequences. The parallel ACK/NACK channels per slot (normal CP) equals to 3×12=36. This number equals to the number of RS symbols transmitted on PUCCH during one slot.
To the inventors' knowledge there is no specific proposals regarding open loop transmission diversity transmission in the UL for the PUCCH. The well-known Alamouti scheme (used e.g., in the DL of WCDMA systems) can be applied between two consecutive OFDMA symbols. However, as mentioned this technique cannot be used on the PUCCH, due to the fact that the available symbol space has been used to separate different UEs.